August in the hills with Chris Horne and Barbara Mitcalfe

Lophozonia menziesii, silver beech, tawhai

Scientists at the Allan Herbarium, Landcare Research, Lincoln, have reclassified the New Zealand members of the beech genus Nothofagus into two genera, using analyses of DNA sequences and morphology. Under this new classification, the NZ beeches are:

Who hasn’t been impressed by the twisted, gnarled, moss and lichen-covered multiple trunks of silver beech trees in the cloud-forest near Alpha Hut? They can grow to 30 m tall, with trunks to 2 m in diameter. The common name comes from the bark, which is silver-grey, particularly on young trees. They grow in montane forest and subalpine shrubland from Coromandel Peninsula through the North and South islands, mostly on the wetter sides of the ranges, and down to sea level in the far south. They are absent from Mt. Taranaki and the Ruahine Range.

Silver beech leaves stay on the tree for several years, unlike those of the other NZ beech species, which retain their leaves for only a year. The dark-green, alternate leaves are rounded, thick, 6-15 x 5-15 mm, with small, rounded teeth. Tawhai is ‘monoecious’, meaning that its small, inconspicuous female and male flowers grow on the same tree. The wind transfers the pollen from the male flowers to the female flowers, which produce hard, dry, 'nuts', c. 5 mm long, each with two or three 'wings' to facilitate wind dispersal.

'Lophozonia' – (crested zone) - refers to parts of the fruiting structure; ‘menziesii’ refers to Archibald Menzies (1754-1842), surgeon with Capt. George Vancouver on the Pacific voyages of the ship ‘Discovery’.

About every three years, like the other NZ beech species, silver beech has a good flowering year, called a mast year, but it does not flower at all in some years. This winter, DOC’s massive programme of aerial 1080 pest/animal poison distribution coincides with the present, NZ wide, mast year. The enormous volume of seed falling from the country’s beech trees is causing an explosion in the numbers of rats in our native forests. Once this bountiful food source is eaten, hungry rats and stoats will resort to killing hundreds of thousands of native birds, lizards and invertebrates, possibly causing extinctions. This pattern of wanton killing has been continuing since ship rats and stoats were introduced in the 1800s.

Use

Māori obtained a black dye from tawhai, for colouring tī kōuka / cabbage tree and flax leaves used in weaving. The dried bark contains about 7% tannin, and was the main source of bark used by a Nelson tannery. We have not found any mention of tawhai having rongoā properties.

The timber is strong but rots when exposed to the weather. However, it is one of our better timbers for steam-bending. Coopers used to bend it into shape to make tubs, baskets and wine casks. Its attractive grain and pale pink to deep-red colour make it popular for furniture and wood-turning.

In the following editions of The Tramper we plan to describe the other four NZ beech species.
We thank David Ogilvie, who requested a description of the re-naming of the NZ beech species.